Static color shift cathode ray tube having control for shifting color at time after the pattern picture changes



y 1970 w. F. ABBOTT STATIC COLOR SHIFT CATHODE RAY TUBE HAVING CONTROLFOR SHIFTING COLOR AT TIME AFTER THE PATTERN PICTURE CHANGES Filed D60.16, 1966 W I 0 FIG 3 H64 I? l2\ l2 20 g\\\\ 2O k 22 H 22 r 2 W 24 --24wwmmqw )4aom mv/m' 46 46 46 \46 FIGS FIG 6 FIG] INVENTOR WILLIAM EABBOTT ATTORNEYS United States Patent 3,514,657 STATIC COLOR SHIFTCATHODE RAY TUBE HAVING CONTROL FOR SHIFTING COLOR AT TIME AFTER THEPATTERN PICTURE CHANGES William F. Abbott, Homer, Alaska, assignor, bymesne assignments, to Parke, Davis & Company, Detroit, Mich., acorporation of Michigan Filed Dec. 16, 1966, Ser. No. 602,236 Int. Cl.H01j 29/26 US. Cl. 313-92 '10 Claims ABSTRACT OF THE DISCLOSURE A staticcolor-shift cathode ray tube having the characteristics otherwisegeneral to a black annd white cathode ray tube, being provided with twoor three phosphor films having the elements thereof being presented withchanges in voltage-dwell timev or frequency repetition ratecharacteristics of the beam, so that a static charge is derived from thevoltage-dwell time characteristics in response to energization of thecontrol layer electrode to shift the production of the static charge tothe phosphor film receiving the beam at an element next adjacentbeamward, and in this way produce a static charge, each of the staticcharges producing and emitting a color characteristic of the phosphormaterial. The control layer electrode may be of resistive dielectricmaterial such as semiconductive material including titanium dioxide (TiOor silicon monoxide (SiO)., and a spatially-disposed screen orconductive layer segments of wire such as platinum may also be disposedin constructing the control layer electrode.

The present invention relates to cathode ray tubes in which the trace onthe face thereof changes color dependent upon the voltage-dwell timecharacteristics of its beam, or the number of times an electron beamtraverses the same spot on the screen within a given short period oftime, and more particularly the invention relates to a cathode ray tubefor color image reproduction having a plurality of phosphor layers ofluminescent material on the screen thereof in which the respectivephosphor films may present a color image depending upon the voltagedwelltime that an electron beam provides for an accumulation of an electricalcharge from the beam in response to increased voltage-dwell timecharacteristics, or a relatively frequent repetition rate for developinga charge on one layer and tending to repel the penetration of the beambeyond said charged layer, and thus illuminate that phosphor film withits characteristic color.

It is therefore an object of the present invention to providemulti-color screens for cathode ray tubes in which the simplicity of theelectronics and the construction thereof is a substantial improvementover the prior art.

Another feature of the invention is that the screens of the inventionmay be used for producing vivid colors in various existing scanconversion and storage tubes with little change in the tube design,including providing the screens of the invention in rebuilt tubes, andalso using the same signal inputs that are presently used for producinghalf tones.

Another object of the invention is that simple cathode ray tubes may beused with the invention for providing color displays that are producedby multiple guns or with a single gun focused by a mesh provided nearthe screen and modulated by post-gun acceleration.

It is a further object of the invention to provide a static charge colorshift cathode ray tube arrangement in which the system of phosphorlayers or films is provided on the face of the cathode ray tube in whicha beam is 3,514,657 Patented May 26, 1970 provided to impinge upon oneof the phosphors as controlled by a charge control layer which providesan accumulated charge for impeding the beam from traversing beyond theaccumulated charge of the phosphor layer, by which the accumulatedcharge repels the beam from penetrating beyond the charged phosphorlayer. The amount of the accumulated charge is dependent upon avoltagedwell time or frequency repetition rate of the beam of aparticular selected point, element or zone on the charge control layer.By controlling the amount of accumulated charge in the control layer, alarge voltage-dwell time or frequency repetition of the charge controllayer repels the beam and restricts the penetration of the beam to theelements to the next adjacent phosphor layer, and which charged filmelement may emit a color such as green. A moderate dwell time oroccasional repetition of the charge control layer provides for a smallcharge accumulation and permits the beam to penetrate to the secondphosphor layer which may emit a color such as blue. A short dwell timeor substantially no repetition of sweep of the beam over the selectedzone of the charge control layer provides for no accumulated charge inthe control layer so that the beam will penetrate to the layer or filmmost distant from the gun and provide a color which may be selected asred. The colors may :be combined and selected so that all the colors ofthe visible spectrum may be accordingly produced.

A complete understanding of the invention may be had from the followingdescription of a particular embodiment of the invention. In thedescription, reference is made to the accompanying drawings of which:

FIG. 1 is a schematic diagram of a cathode ray tube embodying a controllayer, several phosphor layers, and other conventional components of acathode ray tube in accordance with the system of the present invention;

FIG. 2 shows a broken away portion of a portion of a cathode ray tube inwhich three phosphor layers are provided to produce the color imagewhile the back phosphor layer acts as a charge control layer, inaccordance with another embodiment of the present invention;

FIG. 3 shows a broken away portion of a screen of a cathode ray tube inschematic form in which three phosphor layers and a resistive dielectriccontrol layer are provided in accordance with another embodiment of theinvention;

FIG. 4 shows a broken away portion of a schematic diagram of a cathoderay tube in which three layers of phosphor film are used with a controllayer of metal mesh being spatially disposed with respect to thephosphor layers for producing the improved color image in accordancewith another embodiment of the invention; and

FIGS. 5, 6 and 7 show other embodiments of the invention using variouscontrol layer or grid arrangements in accordance with other embodimentsof the invention.

Referring now to the drawings, there is shown a cathode ray tube 10having a display surface or screen 12, and in which at the distal endthereof are mounted electrical connections for the plug 14, from whichis mounted and supported the writing gun 16, and the deflection system18. Conventional collimating system may be provided depending upon thespace and parameters of the size of the tube, as required.

On the interior surface of the display or screen 12 there is a firstphosphor film or layer 20 that may be chosen so that upon it receiving aspace charge from the gun 16, and upon the necessary creation of suchcharge by voltage-dwell time of the beam on a particular element of saidphosphor layer 20, or due to the frequency repetition ratecharacteristics of the beam over such element as the layer, the phosphorlayer will emit its characteristic color, which in one case may be ared.

Similarly, a continuous phosphor layer of luminous material in the formof a film or laminar form is superimposed upon layer 20, the layer 22being selected to emit a color such as a green, and a third or backphosphor layer or film 24 is selected so that is similarly will emit ablue.

Superimposed on the back phosphor layer 24 there is shown in FIGS. 1 and3 a resistive-dielectric charge control layer electrode 30 which may bea thin metal or dielectric film of a material such as evaporated gold,titanium dioxide (TiO silicon monoxide (SiO), or other type ofsemiconductive material, defined in its general sense. Also, thematerial may be a mixture of controlled conductivity and dielectricproperties, such as platinum and quartz, for effecting a control of thetime constant and resolution characteristics of the cathode ray tubesometimes known as semiconductor material.

FIG. 2 shows phosphor layers 20, 22, 24, each which emits light of adifferent color. The back phosphor layer electrode 24 may also functionas a charge control layer due to its ancillary characteristic of havingthe properties of a resistive-dielectric material. While FIG. 2 showsthe back phosphor layer electrode 24 performing the function and actingas a charge controlled layer elec trode, FIG. 4 demonstrates anembodiment in which there is a metal mesh screen 34 that is disposedcontinuously across the width of the cathode ray tube at the point whereit is spatially disposed from the free surface of phosphor layer 24. Inorder to orient electrically the relationship between the phosphor layerelectrode 24 and the metal mesh or screen 34, a variable resistance 36is connected between them.

The layers 20, 22 are of transparent material, and layers 24 as well asthe charge control layer 30 may also be transparent if desired. Thetransparent layers allow light emitted from the back layer to be clearlyvisible through the face of the tube. The back layer 24 need not betransparent, but it needs to be sufficiently thin enough so that anelectron beam of normal voltage used in cathode ray tubes, such asvoltages from 2 to .20 kv. may penetrate completely through tosucceeding layers without being repelled. The back phosphor layer 24 orthe resistive-dielectric control layer electrode 30 acts as a dielectricto accumulate a charge from the electron beam. See FIGS. 1, 2 and 3.This charge tends to repel the electron beam and to prevent the beamfrom penetrating beyond the back phosphor layer. This charge controllayer 30 may be of one of various materials which have the properelectrical conductivity or resistivity and dielectric properties such astitanium dioxide (TiO silicon monoxide (SiO), or it may for example be avery thin layer of a metal such as gold or aluminum. The back layer mayalso be a compound such as containing a material as stannous oxide (SnO)with the oxygen content controlled by the proper ratio or withcontrolled impurity levels or it may be a mixture of chemical compoundssuch as silicon monoxide (SiO) with (SnO). The back phosphor layer alsofunctions therefore as a charge control layer.

FIGURE 4 shows a metal mesh electrode 34 mounted very close to the faceof the screen 12 and with proper biasing with respect to the screenpotential, could act to accelerate or to repel the beam and could inaddition act to collect charges from the screen or to intensify thecharge accumulation on the screen. The metal mesh screen 34, or thecontrol layer 30 may be connected to a reference or ground potentialsuch as by conductor 42.

The charge control layer electrodes 30 and 34 are constructed to becontinuous over the entire surface of the tube, as shown, or, asillustrated in FIGS. 5, 6 and 7, the charge control layer 46, may beapplied in small segments or strips that are parallel to each other anddisposed across the face of the screen. FIG. 6 shows the added featureof providing a continuous conductive layer, more precisely, asemi-conductive layer of resistive-dielectric material disposedcontinuously across the face of the tube, while dielectric layer isshown in segments 46, 46. Further, FIG. 7 contemplates providing smalldots or squares, 4641, as an alternative arrangement so that the dots orsquares are arranged in a grid structure to present a fine screenpattern that is continuously across the face of the tube. The principleis satisfied and remains the same that a charge control layer electrode30 with or Without an adjacent metal mesh control electrode 34, 46, 46a,controls the charge accumulation of the phosphor layers 20', 22, 24which in turn controls the depth of penetration of the electron beam 50and to the multiple layers of phosphor, and thereby controls the colorsemitted.

The composition and physical structure of the charge layer are theparameters which vary the details and requirements of resolution andvoltage-time constant of the tube.

The tube is operated at a beam voltage which when not repelled wouldpenetrate to the front phosphor layer 20 in contact with the screen face12 and the tube would display a trace of the color emitted by thatphosphor layer, which in FIG. 1 where the electron beam 52 penertates tothe phosphor layer 20, the tube would display a trace of the color red.If the beam is allowed to dwell on the same spot 54, or if it sweepsrepetitively across the same spot for a number of times in asubstantially short period, the phosphor layer accumulates a staticcharge on said element or spot 54 from the beam in response to increasedvoltage-dwell time or frequency repetition rate characteristics that thespot will accumulate a charge which tends to repel the beam untilfinally the beam can penetrate only to the next layer 22 of phosphor andthe tube will display at that spot only the color emitted by this backphosphor layer. Then if the beam 56 is allowed to dwell on the same spotsimilarly on element 58 of phosphor layer 22 to increase thevoltage-dwell time or frequency repetition rate characteristics over theelement 58 of layer 22, that element 58 will accumulate a charge whichtends to repel the beam until finally the beam can penetrate only to thelayer 24 and a tube screen will display at that spot or element 58 onlythe color emitted by this back phosphor layer 24. Thus, as the beamsweeps across the tube, and where elements such as 54, 58 where a chargehas accumulated from previous beam sweeps, the display on the screen 12will be in one color for each of the layers 20, 22, 24, and at spotswhere no charge has accumulated from previous beam sweeps, the displayscreen 12 will be in another color where the beam has impinged on one oflayers 20, 22, 24. With the number of layers shown and with the propercharacteristics of the charge control layer electrode 30, several colorsmay be generated showing different numbers of repetitive sweeps ordifferent lengths of voltage-dwell time of the beam.

The voltage-dwell time or number of repetitive sweeps seem necessary toaccumulate sufficient charge for maintaining the beam from penetratingbeyond the back phos phor layer electrode and may be varied over widelimits by the characteristics of the charge control layer electrode. Forexample, a layer electrode having the low conductivity and highdielectric constant of many phosphors will accumulate charge veryrapidly and prevent the beam from penetrating beyond the back phosphorlayer in a small fraction of a second. At the other extreme, if the backphosphor is coated with a thick layer of stannous oxide (SnO),sufiicient static charge never accumulates sufficiently to repel thebeam 50 from penetrating the phosphor layers 20, 22, 24. Between thesetwo extremes, the rate of charge accumulation may be controlled by thecharacter of the control layer and the auxiliary metal mesh electrodesuch as electrode 34 mentioned above so that the period ofdistinguishing between repetitive sweeps and non-repetitive sweeps maybe varied from a small fraction of a second to several minutes.

It is contemplated within the present invention to provide a tubestructure as is described here in which it is possible to achieve colorshifts in a simple fashion by varylng only the voltage-dwell time andrepetition rates characteristics for achieving static color shifts in acathode ray tube. This is contrasted to the prior art where use ofmultiple layers are thin, substantially transparent phosphors to inducecolor changes in cathode ray tubes is well known, in which the colorshift depended on changing the beam voltage or the angle at which thebeam penetrated the phosphor layers, or by a complex combination ofmodulating the voltages and current levels in a tube or plural gunstorage tube system.

Additional embodiments of the invention in this specification will occurto others and therefore it is intended that the scope of the inventionbe limited only by the appended claims and not by the embodimentsdescribed hereinabove. Accordingly, reference should be made to thefollowing claims in determining the full scope of the invention.

What is claimed is:

1. A cathode ray tube for color image reproduction comprising aplurality of continuous phosphor layers of luminescent material in filmor laminant form superimposed upon each other upon the face of saidcathode ray tube, each of said phosphor layers being adapted to produceone of a plurality of different predetermined colors in response toreceiving a static charge on an element derived from voltage-dwell timecharacteristics of the beam of said cathode ray tube, a charge-controllayer electrode formed of a composite of controlled conductivitymaterial and a material of dielectric properties being disposed betweensaid layers of luminescent material and a cathode of said cathode raytube and in close proximity to the free surface of one of said layersuniformly to prevent excessive charge collection and to drain off thecharge that would collect on said phosphor layers, each of said phosphorlayers having substantially the same build-up and decay rates, but eachof said phosphor layers capable of accumulating said static charge onsaid ele ment from the beam in response to increased voltagedwell timeor frequency repetition rate characteristics of the beam over a zone ofsaid layer and at times to repel further charging from said beam, saidstatic charge being in response to energization of the control layerelectrode to shift the color from the element of the phosphor or layerreceiving the charge to the element of the phosphor layer next adjacentbeamward, said charge tending to repel the penetration of the beamtherebeyond and thus illumine the phosphor layer adjacent the charge forallowing penetration of the beam from the cathode until thevoltage-dwell time or frequent repetition of the beam produces anaccumulated charge in a layer for blocking or terminating penetration ofthe beam.

2. The cathode ray tube of claim 1 wherein the phosphor film adjacentthe face of the cathode ray tube is also a charge control layerelectrode for developing a capacitive relation with the other layerelectrode.

3. The cathode ray tube of claim 1 wherein the charge control layerelectrode is formed of resistive-dielectric material positioned on asurface of one of the phosphor films.

4. The cathode ray tube of claim 1 wherein said charge control layerelectrode is a metallic mesh screen spatially disposed parallel with oneof the phosphor films and arranged to be biased with respect to one ofthe phosphor films.

5. The cathode ray tube of claim 1 wherein the charge control layerelectrode is a series of parallel disposed conductive layer segmentsdisposed on a surface of one of the phosphor films.

6. The cathode ray tube according to claim 1 wherein the charge controllayer electrode is a conductive layer continuously disposed over thesurface of one of the phosphor films, and a dielectric layer issegmentally disposed in elements across the conductive layer thereof.

7. The cathode ray tube according to claim 1 wherein the charge controllayer electrode comprises alternate elements of conductive anddielectric components in the order of one mil in thickness dimension forproviding control of time constant and resolution comparable to the dotstructure and spacing of color image reproduction.

8. The cathode ray tube according to claim 3 wherein theresistive-dielectric material is a material selected from the groupconsisting of TiO and silicon monoxide.

9. The cathode ray tube according to claim 4 wherein the screen isplatinum.

10. The cathode ray tube according to claim 5 wherein the segments areplatinum.

References Cited UNITED STATES PATENTS 2,440,301 4/ 1948 Sharpe 31392 X2,446,248 8/ 1948 Shrader 31392 2,446,764 8/1948 Henderson 313-923,284,654 11/ 1966 Bramley et al. 31392 2,566,713 9/ 1951 Zworykin.2,958,002 10/1960 Cusano et al. 3,242,260 3/1966 Cooper et al. 3,284,66211/1966 Kagan. 3,3 30,990 7/ 1967 Guillette.

FOREIGN PATENTS Ad. 68,897 2/ 1958 France.

JAMES W. LAWRENCE, Primary Examiner V. LAFRANCHI, Assistant Examiner

